code: def image_batch(request, channels_first):
      """
      Image fixtures of shape NHWC and NCHW.
      """
      channels = request.param
      image_input = DataGenerator(channels_first, channels)
      test_input = image_input.get_data()
      test_output = test_input.copy()
      return test_input, test_output
  
file_path: adversarial-robustness-toolbox/tests/defences/preprocessor/test_jpeg_compression.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  import numpy
  import pytest
  from numpy.testing import assert_array_equal
  from art.config import ART_NUMPY_DTYPE
  from art.defences.preprocessor import JpegCompression
  from tests.utils import ARTTestException
label_desc: Use image node_id 1 for calling a global function with example usage: image_batch(request, channels_first) and returns: test_input,  test_output